HFIR, the High Flux Isotope Reactor at Oak Ridge (USA)

The High Flux Isotope Reactor (HFIR) is a research reactor located at Oak Ridge National Laboratory (ORNL) in Tennessee, USA.

Commissioned in 1966 with 85 megawatts, the HFIR is the highest flux reactor-based research neutron source in the United States and provides one of the highest steady-state neutron fluxes of any research reactor in the world.

The thermal and cold neutrons produced by HFIR are used to study physics, chemistry, materials science, engineering, and biology.

This reactor with an intense neutron flux, a constant power density, and constant length fuel cycles is used, every year, by more than 500 researchers to study neutron scattering in the fundamental properties of condensed matter.

The reactor is moderated and cooled by light water and uses highly enriched uranium-235 as fuel. The operating cycles in HFIR last approximately 25 days and are typically seven cycles per year, and refueling the reactor is an extensive and complicated process that takes approximately 26 days.

To increase its lifetime beyond 2050, the replacement of the beryllium reflector is planned. The planned shutdown for this task will provide an opportunity to install a cold source in the HB-2 radial beam tube, which would provide an unparalleled flux of cold neutron power.

The neutron scattering research facilities at HFIR contain a collection of world-class instruments used for fundamental and applied research on the structure and dynamics of matter.

Key isotopes routinely produced at HFIR include californium-252, nickel-63, selenium-75, actinium-227 and strontium-89.

HFIR is also used for medical, industrial, and research isotope production; research on severe neutron damage to materials, and neutron activation analysis to examine trace elements in the environment. In addition, the building houses a gamma irradiation facility that uses spent fuel assemblies and can provide high gamma doses for studies of the effects of radiation on materials.

Recent discoveries, made possible by neutrons in HFIR, are helping to unlock the secrets of materials and energy. This new knowledge is also leading to improvements in everyday products such as solar cells, hard disks, medicines, and biofuels. In addition, HFIR capabilities help solve crimes, and isotopes produced in HFIRs are driving the discovery of new elements and spaceflight.

Some fun facts about the HFIR:

• The reactor core is small but powerful

The HFIR produces one of the highest neutron fluxes in the world despite its core being about 2 feet tall and 15 inches in diameter. Its unique design consists of curved fuel plates and a centralized orifice to trap the thermalized neutrons inside the reactor, which is cooled by water at a flow rate of almost 16,000 gallons per minute.

• Research does not always take place in the reactor.

The neutrons can be directed into one of four horizontal beam tubes in the reactor for specialized experiments outside the reactor.

• Can be heated or cooled

HFIR can produce thermal or cold neutrons for everything from physics and chemistry to materials science and engineering.

• Is a leading supplier of Californio-252

HFIR is the only supplier of californium-252 in the Western world. This isotope is used for well logging and industrial scanning. It was also used to treat cancer and detect explosives, but was later replaced by actinium-227 (cancer) and nickel-63 (explosives), isotopes also manufactured at HFIR.

• It will help boost future space missions

Oak Ridge and Idaho National Laboratory are working with NASA to produce about 1.5kg of plutonium-238 per year for future space missions. HFIR irradiates neptunium oxide to create plutonium-238.

• Determined the cause of death of U.S. President Zachary Taylor

Using HFIR, researchers were able to examine samples of President Zachary Taylor's hair and fingernails and determined that arsenic levels were much lower than would be associated with poisoning, ending one of the theories in the debate about his death in 1850.

• Helped discover a new element

HFIR's cold-source capabilities were used to discover element 117 in 2010. The element was officially named tennessine seven years later by the International Union of Pure and Applied Chemistry.